Intercept slice operations in Python

I want to imitate a normal python list, except whenever elements are added or removed via slicing, I want to 'save' the list. Is this possible? This was my attempt but it will never print 'saving'.

class InterceptedList(list):

    def addSave(func):
        def newfunc(self, *args):
            func(self, *args)
            print 'saving'
        return newfunc

    __setslice__ = addSave(list.__setslice__)
    __delslice__ = addSave(list.__delslice__)

>>> l = InterceptedList()
>>> l.extend([1,2,3,4])
>>> l
[1, 2, 3, 4]
>>> l[3:] = [5] # note: 'saving' is not printed
>>> l
[1, 2, 3, 5]

This does work for other methods like append and extend, just not for the slice operations.

EDIT: The real problem is I'm using Jython and not Python and forgot it. The comments on the question are correct. This code does work fine in Python (2.6). However, the code nor the answers work in Jython.